The inkjet printing device of continuous type is configured to continuously jet the ink from the nozzle to charge jetted ink particles in the air, and further deflect the charged ink particles in the electric field so as to perform printing. The inkjet printing device of the aforementioned type has been widely distributed for various purposes of printing numbers and codes on the metal can or the plastic surface.
Patent Literature 1 discloses the inkjet printing device of the aforementioned type as related art. The inkjet printing device includes a main body, a print head, and a conduit for connecting the main body and the print head. The main body is provided with an ink container for storing the ink, a feed pump for feeding the ink from the ink container to the print head, a collection pump for collecting the ink from the print head to the ink container, and a control unit for controlling operations of the printing device.
The print head includes a nozzle that jets the ink fed from the main body in the form of ink particles, a charge electrode for charging the ink particles, a deflection electrode for deflecting the charged ink in the electrostatic field, and a gutter for catching the unused ink. A tube through which the ink flows, and an electric wiring for transmitting an electric signal to the print head are inserted into the conduit that connects the main body and the print head.
The inkjet printing device of continuous type employs the ink solvent with nigh volatility such as methylethyl ketone and ethanol for high speed printing. Upon collection of the ink through the collection pump, the ink is drawn by the gutter along with the ambient air. The thus drawn air is continuously sent into the ink container. It is therefore necessary to discharge the drawn air from the ink container.
The air drawn along with the ink contains volatilized solvent. Therefore, the air drawn by the gutter will be discharged outside the inkjet printing device along with the ink solvent. As the ink solvent is discharged, the ink density becomes high. It is therefore necessary to add the solvent from the solvent container by the amount corresponding to the volatilization amount. The added amount of the solvent is determined in accordance with measured density of the ink in the ink container.
In this way, discharge of the air drawn by the gutter outside the inkjet printing device may apply loads on the environment, leading to increased running costs.
Patent Literature 2 discloses the inkjet printing device including the exhaust line for sending the air discharged from the ink container to the gutter for the purpose of suppressing volatilization of the ink solvent to foe discharged outside the inkjet printing device. The inkjet printing device is configured to circulate the exhaust gas sent to the gutter in the inkjet printing device, thus reducing the ink solvent volatilization amount. The inner temperature of the main body provided with the ink container becomes higher than the inner temperature of the print head by approximately 10° C. to 20° C. under the heat generated by the circuit substrate. Therefore, the exhaust gas temperature is lowered during carriage of the exhaust gas to the gutter, resulting in liquefaction of the solvent.
It is therefore necessary to separate the liquid from the exhaust gas. The separation technique is employed as the gas-liquid separator as disclosed in Patent Literature 3, which is configured to collect the liquid component dripped by gravity.